Commit 69923208 authored by Matthias Maennich's avatar Matthias Maennich Committed by Jessica Yu
Browse files

symbol namespaces: revert to previous __ksymtab name scheme 



The introduction of Symbol Namespaces changed the naming schema of the
__ksymtab entries from __kysmtab__symbol to __ksymtab_NAMESPACE.symbol.

That caused some breakages in tools that depend on the name layout in
either the binaries(vmlinux,*.ko) or in System.map. E.g. kmod's depmod
would not be able to read System.map without a patch to support symbol
namespaces. A warning reported by depmod for namespaced symbols would
look like

  depmod: WARNING: [...]/uas.ko needs unknown symbol usb_stor_adjust_quirks

In order to address this issue, revert to the original naming scheme and
rather read the __kstrtabns_<symbol> entries and their corresponding
values from __ksymtab_strings to update the namespace values for
symbols. After having read all symbols and handled them in
handle_modversions(), the symbols are created. In a second pass, read
the __kstrtabns_ entries and update the namespaces accordingly.

Fixes: 8651ec01 ("module: add support for symbol namespaces.")
Reported-by: default avatarStefan Wahren <stefan.wahren@i2se.com>
Suggested-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: default avatarWill Deacon <will@kernel.org>
Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: default avatarMatthias Maennich <maennich@google.com>
Signed-off-by: default avatarJessica Yu <jeyu@kernel.org>
parent 9ae5bd18

include/linux/export.h

+5 −9
Original line number Diff line number Diff line
@@ -18,8 +18,6 @@ extern struct module __this_module; 
#define THIS_MODULE ((struct module *)0)

#endif



#define NS_SEPARATOR "."



#ifdef CONFIG_MODVERSIONS

/* Mark the CRC weak since genksyms apparently decides not to

 * generate a checksums for some symbols */
@@ -48,11 +46,11 @@ extern struct module __this_module; 
 * absolute relocations that require runtime processing on relocatable

 * kernels.

 */

#define __KSYMTAB_ENTRY_NS(sym, sec, ns)				\

#define __KSYMTAB_ENTRY_NS(sym, sec)					\

	__ADDRESSABLE(sym)						\

	asm("	.section \"___ksymtab" sec "+" #sym "\", \"a\"	\n"	\

	    "	.balign	4					\n"	\

	    "__ksymtab_" #ns NS_SEPARATOR #sym ":		\n"	\

	    "__ksymtab_" #sym ":				\n"	\

	    "	.long	" #sym "- .				\n"	\

	    "	.long	__kstrtab_" #sym "- .			\n"	\

	    "	.long	__kstrtabns_" #sym "- .			\n"	\
@@ -74,16 +72,14 @@ struct kernel_symbol { 
	int namespace_offset;

};

#else

#define __KSYMTAB_ENTRY_NS(sym, sec, ns)				\

	static const struct kernel_symbol __ksymtab_##sym##__##ns	\

	asm("__ksymtab_" #ns NS_SEPARATOR #sym)				\

#define __KSYMTAB_ENTRY_NS(sym, sec)					\

	static const struct kernel_symbol __ksymtab_##sym		\

	__attribute__((section("___ksymtab" sec "+" #sym), used))	\

	__aligned(sizeof(void *))					\

	= { (unsigned long)&sym, __kstrtab_##sym, __kstrtabns_##sym }



#define __KSYMTAB_ENTRY(sym, sec)					\

	static const struct kernel_symbol __ksymtab_##sym		\

	asm("__ksymtab_" #sym)						\

	__attribute__((section("___ksymtab" sec "+" #sym), used))	\

	__aligned(sizeof(void *))					\

	= { (unsigned long)&sym, __kstrtab_##sym, NULL }
@@ -115,7 +111,7 @@ struct kernel_symbol { 
	static const char __kstrtabns_##sym[]				\

	__attribute__((section("__ksymtab_strings"), used, aligned(1)))	\

	= #ns;								\

	__KSYMTAB_ENTRY_NS(sym, sec, ns)

	__KSYMTAB_ENTRY_NS(sym, sec)



#define ___EXPORT_SYMBOL(sym, sec)					\

	___export_symbol_common(sym, sec);				\

scripts/mod/modpost.c

+18 −15
Original line number Diff line number Diff line
@@ -348,18 +348,11 @@ static enum export export_from_sec(struct elf_info *elf, unsigned int sec) 
		return export_unknown;

}



static char *sym_extract_namespace(const char **symname)

static const char *namespace_from_kstrtabns(struct elf_info *info,

					    Elf_Sym *kstrtabns)

{

	char *namespace = NULL;

	char *ns_separator;



	ns_separator = strchr(*symname, '.');

	if (ns_separator) {

		namespace = NOFAIL(strndup(*symname, ns_separator - *symname));

		*symname = ns_separator + 1;

	}



	return namespace;

	char *value = info->ksymtab_strings + kstrtabns->st_value;

	return value[0] ? value : NULL;

}



static void sym_update_namespace(const char *symname, const char *namespace)
@@ -600,6 +593,10 @@ static int parse_elf(struct elf_info *info, const char *filename) 
			info->export_unused_gpl_sec = i;

		else if (strcmp(secname, "__ksymtab_gpl_future") == 0)

			info->export_gpl_future_sec = i;

		else if (strcmp(secname, "__ksymtab_strings") == 0)

			info->ksymtab_strings = (void *)hdr +

						sechdrs[i].sh_offset -

						sechdrs[i].sh_addr;



		if (sechdrs[i].sh_type == SHT_SYMTAB) {

			unsigned int sh_link_idx;
@@ -689,7 +686,6 @@ static void handle_modversions(struct module *mod, struct elf_info *info, 
	enum export export;

	bool is_crc = false;

	const char *name;

	char *namespace;



	if ((!is_vmlinux(mod->name) || mod->is_dot_o) &&

	    strstarts(symname, "__ksymtab"))
@@ -762,10 +758,7 @@ static void handle_modversions(struct module *mod, struct elf_info *info, 
		/* All exported symbols */

		if (strstarts(symname, "__ksymtab_")) {

			name = symname + strlen("__ksymtab_");

			namespace = sym_extract_namespace(&name);

			sym_add_exported(name, mod, export);

			sym_update_namespace(name, namespace);

			free(namespace);

		}

		if (strcmp(symname, "init_module") == 0)

			mod->has_init = 1;
@@ -2061,6 +2054,16 @@ static void read_symbols(const char *modname) 
		handle_moddevtable(mod, &info, sym, symname);

	}



	/* Apply symbol namespaces from __kstrtabns_<symbol> entries. */

	for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {

		symname = remove_dot(info.strtab + sym->st_name);



		if (strstarts(symname, "__kstrtabns_"))

			sym_update_namespace(symname + strlen("__kstrtabns_"),

					     namespace_from_kstrtabns(&info,

								      sym));

	}



	// check for static EXPORT_SYMBOL_* functions && global vars

	for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {

		unsigned char bind = ELF_ST_BIND(sym->st_info);

scripts/mod/modpost.h

+1 −0
Original line number Diff line number Diff line
@@ -143,6 +143,7 @@ struct elf_info { 
	Elf_Section  export_gpl_sec;

	Elf_Section  export_unused_gpl_sec;

	Elf_Section  export_gpl_future_sec;

	char	     *ksymtab_strings;

	char         *strtab;

	char	     *modinfo;

	unsigned int modinfo_len;

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